Lapping scratches...

After last year's discussion about how a DMT 1200 shouldn't be used to lap hones, I've been using a DMT8C. No matter how much I break it in, it still leaves some pretty deep scratches (localized to about 1/4 the total surface, which makes me think I have some "tall" diamonds on the DMT) in whatever I'm lapping.

So I'm wondering... what, if any, effect those scratches would have on the razor edge? I keep going back and forth: yeah, it's gonna degrade the edge, and no, it's not.

The scratches are visible, and you can really feel the difference between the scratched ares of the stones and the unscratched. It makes the hone feel much coarser than it is, as you can imagine.

But as long as the grit of the stone is constant, it shouldn't really matter if there is a VVVVVVV type of texture to the surface, right? As long as the blade is drawn across it in an X pattern, insuring even coverage along the edge, the effect should be the same as a completely smooth surface?

What do you guys think?

I'm tempted to go back to using the DMT8E until it's worn out, just cause it left such a great surface on whatever it lapped.

I've tried using the 1k shapton to get the scratches out, but they're too deep.

I don't think it will affect a razor unless you are using a lot of pressure when honing, in which case the scratches might lead to microchipping.

I figure the only way to get rid of problem areas on the D8C is to work it with something hard and flat. Like barber/Escher/Chinese hones.

But here's a thought. The back of your D8F is hard and flat. If you are willing to lose the nickel coating it would break in the D8C pretty well.

i found an old junk razor works pretty well to break it in and lapping a ch12k...

dab of soap and some water, then go to town.

Good ideas, gents, thanks... I'm going to lap the bejesus out of my Chinese 12k, and the *back* side of the DMT8F with the 8C and see if I can knock those high diamonds down a notch or two.

Edit: I took the 1200 DMT to the 16k and 30k shaptons and removed the scratches. Then I used the 1k shapton to smooth the 16k and the 30k, then I rubbed the 16k and 30k together. The 16 and 30 are back to being completely scratch free and smoooooooth. I wanted to do this months ago, as this has been a problem (or not?) for a while, but I've been recovering from spine surgery, and until recently couldn't rub two nickels together. This is the first time I've lapped my stones since January. They were really dished out.

Pizza,

How much pressure were you using with the DMT's?

I've found that even with the DGLP, which is #325/#375, it leaves scratches on the surface, but no where as deep as it sounds like you are describing.

Unless you are making actual grooves in the surface of the stone, the small scratches shouldn't effect your sharpening. The stone may feel a little more aggressive at first, but the grit of the stone is still the same. Those peaks will wear down quickly on the 16K and 30K stones.

I've just read your last post - sounds like you're doing some serious lapping. Just be careful not to pull out all of the diamonds from your DMT's!

Good luck!:D

Ah ha! I finally found them, them scratches people worry about. I had to hold the hone up in the light just right to get some reflection. I never found need to look at one so:)

You guys will worry ....unless you seeing something way more obvious. lap on. Maybe your fine finishers could be brought up higher which happens auto matic with diamond nagura; rubber-stone too

Are the scratches merely visible and cosmetically unappealing, or can you feel them if you rub a fingernail over them?

If mostly cosmetic, I haven't had any problems with that. If it really bothers me, I will take the stone to 400 and then 800 grit paper.

if you don't like scratches on your hone after dmt try use 400 sandpaper after dmt will clear them up less then 3 minutes.hope this helps

Man.. thanks for the help, everyone. :)

I haven't been using too much pressure, as I simply can't... I still don't have full use of my left arm yet, but it's getting better. Also because the stones get stuck together when using too much pressure. It's just a localized area of the DMT8C that is causing the problem... the majority of the stone being lapped comes out with no scratches, but about 1/4 or less of the surface is scratched. You can feel the scratches with your finger.

I had the same problem with scratches that you did!

I use a DMT D8X to lap, and it leaves pretty bad scratches on hones. So, what I do is use my Chinese 12k as a "smoothing" stone on the hones after I've lapped them. Gets the scratches right out!

See this thread for more info:
Chinese 12K as a Dressing Stone

Take your fingertip and run it around the top edge of your DMT. You may have a divot on the edge. I have had them on more than one of my plates and flattened them out using the shank of a long screwdriver rubbed briskly.

Also you mention the sticking together. Are you lapping in the sink under running water ? If you let swarf build up it might cause the scratches you describe.

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Originally Posted by JimmyHAD

Take your fingertip and run it around the top edge of your DMT. You may have a divot on the edge. I have had them on more than one of my plates and flattened them out using the shank of a long screwdriver rubbed briskly.

Also you mention the sticking together. Are you lapping in the sink under running water ? If you let swarf build up it might cause the scratches you describe.

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Yes.

I found the area on the DMT that has the "high" diamonds. I'm still trying to smooth it out by rubbing it against my chinese 12k.

The "high" area can be felt, but not seen. The hone itself appears to be just like it should, even under magnification. No defects can be seen.

Just a couple of tall diamonds.

Quote:

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Originally Posted by FloorPizza

Just a couple of tall diamonds.

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The solution is simple, remove them and set them in a nice piece of jewelry, and give to the wife/significant other! :D

Good idea, thanks! :)

I *really* wish I had the money to take advantage of your sale on the shapton lapping stone. I have 1k, 4k, 8k, 16k, and 30k Shapton on glass, all subject to the abuse of being lapped by a DMT8C that likes to put scratches in them.

BTW, I *really* like the Shaptons a lot. No regrets on spending the rather significant amount on the set. I do kinda wish I had the 2k stone, though. Jumping from the 1k to the 4k sometimes seems a bit steep.

Quote:

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Originally Posted by FloorPizza

Good idea, thanks! :)

I *really* wish I had the money to take advantage of your sale on the shapton lapping stone. I have 1k, 4k, 8k, 16k, and 30k Shapton on glass, all subject to the abuse of being lapped by a DMT8C that likes to put scratches in them.

BTW, I *really* like the Shaptons a lot. No regrets on spending the rather significant amount on the set. I do kinda wish I had the 2k stone, though. Jumping from the 1k to the 4k sometimes seems a bit steep.

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Floor Pizza - I sent you a PM

Update: I was able to remove the offending tall diamonds with a flat blade screwdriver. It now laps 'em smooooth. The 8c laps sooo much faster than the 8E did. Even my Chinese 12k gave it up quickly to the 8C.

I get rid of lapping scratches left my my DMTC by rubbing the stone I've just lapped with another lapped stone that is hard, fine, and non-porous. I have used my C12K, Swaty's, and a Spyderco pocket stone (the "fine" one) for this, and all have worked quite well. I'm sure most "finishing" or "touch-up" barber hones would do this job well, since they tend to be fine, hard, non-porous and slow.

In theory if a hone were perfectly flat no matter what the grit it would not cut, just as you could make a saw out of the hardest steel in the world and without teeth it would be useless. The scratches will be a problem if it forms a repetitive frequency- where the peaks line up and the valleys line up, which will sawtooth your razor. If they are random circular scratches you'll be fine. The hone has literally millions of scratches and textures and what not at the micro level. Thats what makes it work.

I think the concern is that scratches that are large enough to see indicate peaks and valleys that are larger than normal and which might catch the blade and cause micro chipping. Or at least that is my concern.

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Originally Posted by holli4pirating

I think the concern is that scratches that are large enough to see indicate peaks and valleys that are larger than normal and which might catch the blade and cause micro chipping. Or at least that is my concern.

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Yes, that's it exactly.

Ah I see. yeah then you'll have to take em out with a finer grit progression. If you go to an autostore, they sell a multipack of 3m wet dry that goes like 200 400 600 800 1000. Worked well on my Swaty after I blasted it on the 120 grit.

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Originally Posted by khaos

Ah I see. yeah then you'll have to take em out with a finer grit progression. If you go to an autostore, they sell a multipack of 3m wet dry that goes like 200 400 600 800 1000. Worked well on my Swaty after I blasted it on the 120 grit.

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That's why you need two Swaty's; so you can remove the scratches ;-p

Did you break in your DMT as recommended by DMT? A DMT 325 shouldn't leave scratch marks on a stone. I've been using them for this purpose for years and it doesn't happen to me. It's not that you "shouldn't" use a DMT1200 but that it loads really quickly - like after 3 or 4 strokes and then it has to be washed out to be useful again. Break in the DMT by rubbing it with a flat piece of steel for about 5 minutes. Use soapy water as the lubricant.

Quote:

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Originally Posted by Howard

Did you break in your DMT as recommended by DMT? A DMT 325 shouldn't leave scratch marks on a stone. I've been using them for this purpose for years and it doesn't happen to me. It's not that you "shouldn't" use a DMT1200 but that it loads really quickly - like after 3 or 4 strokes and then it has to be washed out to be useful again. Break in the DMT by rubbing it with a flat piece of steel for about 5 minutes. Use soapy water as the lubricant.

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Yeah, I'm kinda anal about doing things exact and per instructions. My particular 8C just had a couple of taller-than-normal diamonds that I was able to remove with a screwdriver tip. It now laps great!

Howard, I hate to disagree with someone that has a ton more experience than me, but.... DMT does actually say that you should not use a DMT 1200 to lap with. It really does ruin them. I found this out the hard way last year when I used a 1200 to lap a bunch of stones including my Shaptons. My 1200 is pretty much ruined now; the front side of the hone looks like the back side now. All the diamonds and the material they use to bed the diamonds on the nickel is gone. Well, most of it, anyway.

I believe that hi_bud_gl actually had a conversation with DMT about this subject, and they stated 1200's were not to lap with... let me see if I can find a link to that thread....

Edit: this thread... http://straightrazorpalace.com/advan...w-problem.html contains the information from DMT about what DMT's are suitable for lapping.

Yeah, that thread is what made me get the DMT D8X, definitely glad I went with the coarser one - makes lapping hard stones a cinch!